Among substrate processing apparatuses for manufacturing semiconductor devices, there is a batch-type vertical substrate processing apparatus for stacking and processing a plurality of semiconductor wafers as substrates therein. In general, the batch-type vertical substrate processing apparatus is configured such that a certain number of wafers are sustained as a plurality of layers in a boat serving as a substrate sustaining member at a predetermined interval (wafer stacking interval pitch). Further, the boat sustaining wafers is typically loaded to or unloaded from a reaction tube for constituting a reaction chamber so as to perform a substrate processing process. If the ratio of a distance (gap) between outer edges of wafers and an inner wall of the reaction tube to the wafer stacking interval pitch is relatively large, raw material may not positively flow onto the wafers. Thus, the raw material is unnecessarily wasted which in turn increases costs for film formation. Further, such problem may get worse as the diameter of substrates increases as in recent years.
In an effort to solve the problem, a plurality of solutions is presented. However, some of the solutions are simply related to a technique of preventing an increase in costs for film formation by controlling a supply flow rate of a gas by means of a controller, without considering the problems of the apparatus configuration described above.
Further, a vertical substrate processing apparatus needs gas to be supplied (or gas replacement) or vacuum evacuation more quickly.